


(In)Capable Hands

by alicedragons



Series: Heat Wave [3]
Category: Undertale (Video Game)
Genre: (No clear dom/sub dynamic), Bottom Slim, Explicit Sexual Content, Heat Fic, M/M, Masturbation, Mating Cycles/In Heat, Mild Intrusive Thoughts, Penetrative Sex, Sex Toys, Smut, Top Cash
Language: English
Status: Completed
Published: 2019-01-31
Updated: 2019-01-31
Packaged: 2019-10-19 21:54:14
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,300
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/17609726
Author URL: https://archiveofourown.org/users/alicedragons/pseuds/alicedragons
Summary: Cash has never been anyone's first choice of heat partner. So it comes as a bit of a surprise when Slim asks a favour of him. A favour he's not sure he's entirely capable of fulfilling.





	(In)Capable Hands

**Author's Note:**

> Part 3 of the heat fic series, requested by anon on tumblr. A follow on of the previous fic, though it can act as a standalone. This one is pretty light-hearted. Just Cash being awkward and insecure (and Slim providing reassurance).

As much as Cash loved his job, he was grateful when Slim’s call interrupted him. He was burnt out on paperwork. He balanced the phone between his skull and shoulder as he copied the month’s stats onto his reports. “what’s up, pup?”

“need your help.” Slim’s voice was huskier than normal, and that on its own was enough to give Cash pause. If he’d been smoking, something might be wrong.

“is it urgent?” he asked, feigning indifference. “i’m a little busy.”

“pretty urgent. i’m in heat.”

Cash went still, putting his pen down. “oh... why are you calling me?”

“because i need someone to water my plants while i’m writhing around in pain,” Slim said shortly. “why do you think, idiot? i need a partner.”

Cash scraped a hand over his skull, scowling. “yeah, yeah, i know. but... don’t you usually ask twisted?”

“twist is recovering from a heat.”

“rus?”

“recovering from twist’s heat,” Slim said flatly.

Cash grimaced, tapping his pen on the desk. “... edge?”

“you’re not my last damn resort, cash,” Slim snapped. “i called you because…” He fell silent for a moment, then— “do you not want to help me?” His tone was a touch dejected, and Cash’s soul clenched. “i mean—you know i won’t be upset if—you don’t have to—”

“no,” Cash interrupted. “i mean—yes, i’ll be there.”

Slim sighed. “thanks, man. i appreciate it.”

“yeah.” Cash swallowed and hung up. Leaning back in his chair, he shut his eye. No one ever asked him for help with their heats. He got help from Slim sometimes, but usually he’d go to Grillby, or just hire a fuck for the night. But he was never the go-to for the others when they needed a partner. And he was pretty sure he knew the reason for that.

Cursing himself silently, he grabbed his keys, realising he probably should have asked Slim if there was anything he needed to bring. For good measure, he packed a bag with a change of clothes and a tub of lube. He tossed it onto the passenger seat of his car, studied it, then went back inside to retrieve food—Slim wasn’t so great at keeping his fridge stocked.

And neither was he, apparently. All he could find was a bag of chips and a couple of snack bars. They’d have to suffice. He packed them too before pulling out of the driveway and onto the highway that led downtown.

When he arrived at Slim’s apartment, the door was locked. He was still sane enough to be precautious, that was good. Then again, in a neighbourhood like this, locks on the doors were more important than running water. Cash knocked and waited in the hallway, eyeing the other doors warily. He liked Slim, but when they fucked, it was at Cash’s place, always. Slim’s living arrangements were dismal. In the few times he’d visited here, Cash had seen more strange characters entering and exiting the building than he’d cared to.

When Slim opened the door, the smell hit Cash at once. Sharp and cloying, but warm, inviting. Slim was hunched over slightly, wearing light clothing despite the chill outside. He waved Cash in without making eye contact. “make yourself at home.” Cash walked through the living room, shivering.

“did you actually turn the cooling on?” he asked sourly. Slim just shrugged, making Cash scowl. He eyed the room with distaste. Scattered cans and dirty dishes occupied more space than they ought to, and the cushions from the sofa were on the floor.

Cash turned to Slim, clearing his throat. “so, uh, how far along are you?”

Slim shrugged. “i’m not gone, but far enough. best to fuck it out now before it gets bad.”

“right, yeah.” Cash shoved his hands in his pockets, looking at the carpet instead of Slim’s face. “so, uh, what do you want from me?”

“your stellar personality,” Slim said, rolling his eye-lights.

Cash narrowed his socket. “can you stop being a prick?”

“c’mon,” Slim said, nodding at Cash. “get your clothes off. we’re doing this in the living room. bed’s broken.”

Cash gave the dirty room a bitter look, shrugging off his jacket. “twisted?”

Slim pulled a face and hummed. “what’s in the bag?”

Cash lifted a brow. “just lube and clothes. and snacks.”

Slim’s mouth twitched. “you think a guy like me doesn’t have a drawer full of lube? and a fridge full of leftover pizza?”

Cash scowled and tossed the backpack on the floor. “fine, whatever. we’ll use your stupid lube.”

Slim paused, then picked up the bag. “no—no, let’s use yours.” He gave Cash a small smile. “i appreciate you bringing it.”

Cash looked away, his cheekbones warm. He stripped down to just his jeans and socks, then looked at Slim. “uh, so—mm!” Slim kissed him hard, pressing their bodies flush and grinding into him. He was burning, and there was a fervour to the way he moved. Normally when they fucked, Slim liked to take his time with foreplay, and even a little pre-sex conversation. But in a matter of moments, he had his hand in Cash’s pants. He stroked his pubic symphysis and Cash grunted. His magic rushed to the area to meet Slim’s touches. He broke their kiss for a second. “w-what do you want me to…?”

Slim swallowed his words with another kiss. “just—whatever,” he murmured against Cash’s mouth. “i don’t care.”

Cash would have preferred it if he’d been given a specific direction. After deliberating for a few seconds, he formed a cock and pulled back to look at Slim. “is that o-okay?”

“mhm,” Slim hummed against his mouth, pulling his jeans down. He guided Cash to the sofa, pushing him back. Cash lay down while Slim removed his shirt and pants, then settled between Cash’s knees, kissing him again. When he broke away, Cash noticed a deep set of teeth marks on his collarbone, and a few smaller bites on his ribs.

“twist?” he asked, eyeing them.

Slim tilted his head. “you keep bringing him up. want me to call him over?”

Cash grimaced. “i’m good, thanks.”

Grinning, Slim fumbled around in Cash’s bag on the floor while he ground against him. His cunt was hot against Cash’s cock, and already slick. He paused to unscrew the lid of Cash’s lube, then scraped out a generous portion and slathered it over Cash’s cock. Cash let out a soft groan, his cock hardening in Slim’s hands. He watched as Slim worked him, swallowing. Normally, when he was in heat, Slim took over and pleasured him until the heat was out of him. He lifted himself on his elbows. “hey, you want me to—to…” He eyed Slim’s cunt and Slim lifted a brow.

“go down on me?” Cash gave a small nod and Slim shrugged. “yeah, alright.”

In retrospect, Cash probably could have planned this better. He’d had a lot more practice with blowjobs than he had with cunnilingus, and his talent for it was awkward at best. It wasn’t unusual for Slim to be quiet, but he sighed gently and ran his fingers down the back of Cash’s skull and neck. “yes, that’s it sweetheart,” he breathed. “hah…” Cash pressed his tongue inside him and Slim hummed. “alright, come up, i want you inside me now.” Cash’s chest clenched and he sat up, wiping his mouth.

“you sure? i—i barely got started.”

“i know, love, but i really just need to be fucked, you know?”

Cash nodded glumly. ~~Fuck, had he really been that awful?~~ “yeah, right. i get it.” Regardless of his mild dejection, he was beyond hard at this point, so it was something of a relief to be able to fuck Slim.

He guided his cock between Slim’s folds and slowly inched in. Slim lifted his legs to deepen the angle, shifting and squirming beneath him. “is—is this okay?” Cash asked tentatively. Fuck, Slim was so warm and tight, he just wanted to bury himself in him.

“hm, yeah, it’s good,” Slim said. Taking the words at face-value, Cash leaned over him and pressed his face against Slim’s neck as he pushed deeper. Slim exhaled, his arms tightening around Cash’s shoulders. “you can go faster than that, i’m pretty loose. i prepped myself before you got here.”

In some ways, that stung Cash a little. ~~Did Slim not trust him to do this properly? Was he not caring enough?~~ He pushed those thoughts aside and sank deeper. His cock twitched inside Slim, the tight warmth making magic rush downward. When he was fully seated, he slowly pulled back out, then sank in again with a little more force. He built a steady pace, bracing his hands beneath Slim’s pelvis as he fucked him.

“c’mon cash, harder,” Slim murmured, tightening his legs around his waist. Cash grunted, thrusting in with more vigour. “yeah that’s it, good boy.” He sighed and tipped his head back, exposing his neck. Cash kissed his collarbone and nipped at his shoulder. “little bit harder,” Slim said.

Cash squirmed. “sorry, i just—i don’t want to hurt you.”

“you won’t.” Slim dug his fingers into Cash’s shoulders. “rough is good. i need it.” Nodding, Cash pounded into him and Slim gasped. “ _fuck,_ just like that. just like that, cash, fuck!”

Not that Cash was opposed to a little rough sex, but he wasn’t exactly equipped for it. His climax was building too quickly, only spurred on by Slim’s delicious cries. “fuck, slim, i—fuck, i’m coming…” He buried himself deep inside Slim, clinging to him as he came. Slim kissed his jaw, stroking his fingers down the back of his neck. Cash’s face burned and he dared a glance up. “did you…?”

Slim shook his head and Cash’s insides withered. “not yet.” He lifted Cash off him and got up. Cash wanted to melt into the sofa.

“i’m sorry…”

“hey, don’t sweat it,” Slim said easily. “just wait here, be back in a second.” He disappeared down the passage toward his bedroom, and Cash threw an arm over his face, shame crashing over him. He was supposed to be helping Slim with a heat, and he couldn’t even get him to come! A traitorous part of him wondered if Slim had left to call someone else over. He had mentioned Twist… ~~This had been a big mistake Cash should just have refused when he’d had the chance he wasn’t equipped for this he couldn’t take care of people he was selfish and conceited and--~~

When Slim returned, he lay down next to Cash. He was holding something… ah. The rubber toy was just a tad thicker than Cash—not that he cared to notice such details. Squeezing Cash’s arm, Slim rested his head on his shoulder and sighed, pressing the toy inside himself. Lying against Cash, he fucked himself with the it, moaning quietly. His breaths were heavy against Cash’s shoulder, and he let go of his arm to play with his clit, exhaling as he came. Cash swallowed, his cock twitching as he eyed the toy, still buried inside Slim. Lying back, Slim shut his eyes.

Slowly, Cash sat up. “do you… do you want me to go?”

Slim opened his eyes. “what? no.” He frowned. “you think—you think i’m replacing you with this…?” He eyed the toy, faintly amused. Cash grimaced and wiped a hand over his skull.

“sort of feels like i’m not really helping here.”

Shaking his head, Slim sat up, taking his hand. “your being here is helping. you don’t have to have your dick in me to be useful.” He sighed and rested his head on Cash’s shoulder. Magic suffused Cash, and cautiously, he put an arm around Slim. “it’s always easier having someone to ground you. makes it more pleasurable and less exhausting.” He grunted as he pulled the toy out of himself, handing it to Cash. “you wanna take over?”

Cash nodded eagerly, taking it from him. It was still slick with his magic, and slid easily into him when Cash pushed. He rubbed Slim’s clit while he fucked him with the toy, and Slim buried his face into the crease of Cash’s elbow, panting. “fuck, just like that, yeah—oh fuck, that’s it, sweetheart. right there, you’re doing so well, _oh…_ ” He whined softly as he came, lifting his chin to kiss Cash.

“was that... good?” Cash asked tentatively, holding onto Slim even as they broke away.

“yeah, love,” Slim murmured, resting his head against Cash’s chest with a sigh. “yeah, real good.” Cash’s face warmed, and he preened silently. Slim grinned up at him, wrapping a leg around his waist. “that cock ready for action again?”

Cash’s cock was heavy between his legs, and their closeness made it throb. “yeah,” he said, kissing Slim. “yeah, more than ready.”

 

“hey man, thanks for coming around,” Slim murmured, settling against Cash’s chest. Cash’s bones felt heavy with exhaustion. It hadn’t been a particularly intense heat—they’d only been at it for a couple of hours. But he’d never had much stamina. Most of the last hour had been spent with Slim’s toy in his hand.

“yeah,” he said. “happy to help.”

Slim grinned and kissed his chin. “maybe next time i’ll invite twist to join us. or we could lend him a hand when it’s his turn.”

Cash scowled, flicking the side of Slim’s skull. “lose my number if you’re thinking of doing that. he’s bad enough when he’s not in heat.”

Slim laughed and tucked himself against Cash. “you were good, patches. thanks for being here.” The nickname made Cash frown, but he held Slim close, kissing his skull.

“thanks for letting me help,” he whispered, in a voice too quiet for Slim to hear.

**Author's Note:**

> My tumblr is @dragonfics if you'd like to follow me there! (18+ blog)


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